Hyperfine induced magnetic order in Pr: Neutron diffraction at mK temperatures

Abstract

With elastic neutron scattering we investigated the magnetic reflections of a single crystal of pure Pr in the temperature range down to 8 mK. We found a double peak structure consisting of a narrow antiferromagnetic satellite with incommensurable wave vector and a broad peak of presumably quasielastic origin, as seen in previous measurements at higher temperatures. The saturation of the magnetic moment is almost reached at the lowest temperatures and approaches the theoretical expected value of 0.6 μ_B. Below a temperature of T=40 mK the magnetic moment turns away from the b-axis towards the a-axis of the crystal. Measurements in an external magnetic field indicate 3 domains. A magnetic field along the a-axis bigger than 500 mT destroys the magnetic order.